Choke restrictor devices and methods

ABSTRACT

Flow enhancing restrictors are located within a fluid conduit to provide pressure reduction and flow enhancement. The restrictors may be used in combination with a conventional choke valve or as a stand-alone pressure reduction means. Alternative exemplary embodiments for flow enhancers are described. Each of the flow enhancers has a generally cylindrical base with at least one fluid passage disposed therethrough. Each of the flow enhancers also provides a dome that projects upwardly from the center of the base to assist in directing fluid flow and receiving the abrasive forces associated with the fluid.

[0001] This application claims the priority of provisional UK patentapplication no. 0000279.0 filed Jan. 8, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to devices and methods for reducingfluid pressure and velocity and enhancing fluid flow within a pipe orother flowbore. The devices and methods of the present invention have aparticularly useful application in pipelines where crude oil or naturalgas is flowed which contains abrasive agents.

[0004] 2. Description of the Related Art

[0005] Production pipelines and conduits are used to transmithydrocarbons, in the form of crude oil or natural gas, from a producingwell to a storage facility or distribution point. One important aspectto the design for systems of these conduits is the ability of theconduits to manage fluid pressure and enhance the flow of fluid withinthe conduit. When hydrocarbons first leave the well and enter theconduit they are often under vary high pressure, and this pressure mustbe quickly and efficiently reduced.

[0006] A related problem is that the hydrocarbons, particularly naturalgas, carry sand and other solids that will quickly abrade and/or clogflow reducing restrictions in the conduit. Efficient pressure reductionis necessary to preclude damage to the more vulnerable portions of thepipeline system. In addition, it is important that the pressurereduction means itself is highly resistant to abrasion and other weardamage that will be inflicted by the solids.

[0007] It would be desirable to have devices and methods that addressthe problems of the prior art.

SUMMARY OF THE INVENTION

[0008] Arrangements are described wherein flow enhancing restrictors arelocated within a fluid conduit to provide pressure and velocityreduction as well as flow enhancement. The flow enhancers may be used incombination with a conventional choke valve or as a standalone pressurereduction means. Alternative exemplary embodiments for flow enhancersare described. Each of the flow enhancers has a generally cylindricalbase with at least one fluid passage disposed therethrough. Each of theflow enhancers also provides a dome that projects upwardly from thecenter of the base to assist in directing fluid flow and receiving theabrasive forces associated with the fluid. The dome, in each of theembodiments, assists in directing fluid into the fluid passages of theflow enhancer and also provides a wear surface upon which abrasives arerecieved.

[0009] It is an object of this invention to provide an efficient andlong-lasting method of achieving a pressure drop within a fluid conduit,particularly where highly abrasive fluids are being transmitted. It is afurther object of this invention to provide a fluid flow enhancer devicethat is highly resistant to abrasive action.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010]FIG. 1 is a side cross-sectional view of an exemplary choke valveof the type used within pipelines which incorporates a fluid flowenhancer constructed in accordance with the present invention.

[0011]FIG. 2 is an isometric view of a first embodiment for a fluid flowenhancer.

[0012]FIG. 3 is a side isometric view of a second embodiment for a fluidflow enhancer.

[0013]FIG. 4 is a further isometric view of the fluid flow enhancerillustrated in FIG. 3.

[0014]FIG. 5 is an isometric view of a third, and most preferred,embodiment for a fluid flow enhancer constructed in accordance with thepresent invention.

[0015]FIG. 6 is a plan view of the fluid flow enhancer depicted in FIG.5.

[0016]FIG. 7 is a side cross-section of the fluid flow enhancer shown inFIGS. 5 and 6.

[0017]FIG. 8 illustrates staged enhancers located within a fluid flowconduit to achieve a greater pressure drop.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0018] Referring first to FIG. 1, there is shown an exemplary chokevalve 10 that incorporates a fluid flow enhancer as contemplated by thepresent invention. The choke valve 10 includes a valve body 12 that istypically constructed of a strong and chemically resistant metal. Thebody 12 defines a fluid inlet 14 and fluid outlet 16 which are set atnight angles to one another thereby providing an elbow configuration forthe valve body 12.

[0019] The fluid outlet 16 houses, at its upper end, a stem and tipassembly 20 which is concentrically located within a flow cage 22 thatis set within the body 12. The stem and tip assembly 20 may be movedlinearly within the body 12 by a manual handwheel, via an automatedcontrol, or using other techniques known in the art. Linear movement ofthe stem and tip assembly 20 actuates the choke mechanism 23 of thechoke valve 10. The choke mechanism 23 is used to regulate fluid flowwithin the valve 10 and includes a tip member 26 and surrounding flowcage 22.

[0020] The lower end of the stem and tip assembly 20 is secured byautofrettage at interface 24 to a tip member 26. The tip member 26 is asubstantially cylindrical piece having a central dome-shaped chamber 28.The central chamber 28 is surrounded by a number of fluid flow openingswithin the tip member 26. The fluid flow openings are of differing sizesand are positioned in mutual opposition to one another so that openingsof equal sizes are located directly across from one another. Forexample, fluid flow openings 30 are of equal sizes and are locatedantagonistically from one another. The same is true of openings 32.Openings 34 (one shown) and 36 (one shown) have the same arrangement. Apressure balance chamber 38 is defined within the domed geometry of thetip member 26 and the stem and tip assembly 20. The chamber 28 has anenlarged lower opening 40 that is located across from the pressurebalance chamber 38.

[0021] The flow cage 22 radially surrounds the tip member 26 and isretained within the valve body 12 by a bonnet (not shown) onto a valveseat 46 at its lower end. A valve seat insert 48 is disposed within thevalve seat 46. The flow cage 22 is a tubular member that contains aplurality of radial fluid communication openings 50, four of which areshown. The tip member 26 can be moved upwardly and downwardly within thebody 12 by linear movement of the stem and tip assembly 20 to modulatefluid entry into the chamber 28. Such rotation will align the fluidopenings 49 in the flow cage 22 with various fluid openings 30, 32, 34,36 in the tip member 26 to permit different flow rates into the chokemechanism 23, as those of skill in the art will appreciate.

[0022] A fluid flow enhancer 50 is located within the fluid outlet 16below the valve seat 46. The flow enhancer 50 is retained within theoutlet 16 by a pair of bushings 52 and 54 that are locatedconcentrically on either side of it. Other retention means may also beused. It is pointed out that, while the described embodiment illustratesa flow enhancer 50 incorporated within the valve 10, the flow enhancermight also be of the design of flow enhancer 50′ or 50″, which will bedescribed shortly or another type of flow enhancer falling within thescope of the claims.

[0023] In operation, fluid enters the fluid inlet 14 and encounters thechoke mechanism 23. Fluid enters the fluid openings 49 of the flow cage22 and one or more of the fluid openings of the tip member 26. Becausethe fluid is under pressure, the opposing openings create opposing fluidjets within the chamber thereby effectively creating a fluid pressuredrop. The fluid exits the choke mechanism 23 through the opening 40 andis directed along the fluid outlet 16 to the flow enhancer 50. As thefluid passes through the fluid passages 62 of the flow enhancer 50, afluid pressure drop and fluid velocity reduction is achieved. Ifdesired, there may be multiple flow enhancers 50 located in a stackedrelation downstream from the choke mechanism 23.

[0024] There is a particular advantage in locating one or more flowenhancers 50 immediately downstream from the choke mechanism 23. Fluidvelocities within the flow cage 22 and tip 26 will be reduced. Theintroduction of a pressure drop across the one or more enhancers 50means that the pressure drop through the choke mechanism 23 is reduced.Therefore, the choke mechanism 23 is also subjected to less wear andabrasion from solids. When the flow enhancer 50 is included downstreamof the choke mechanism 23, adjustment will need to be made to the chokemechanism 23 to ensure adequate flow rate exits the flow enhancer 50. Inother words, the choke mechanism 23 will have to be opened somewhat tocompensate for the pressure reduction across the flow enhancer 50.

[0025] The structure of the exemplary fluid flow enhancer 50 is betterunderstood with reference to FIG. 2 wherein this component is shownapart from the check valve 10 and its structure may be seen in greaterdetail. The flow enhancer 50 has a unitary body 58 that is formed of astrong material that is resistant to chemicals and mechanical abrasion.Tungsten carbide and precipitation-hardened stainless steel are twoexamples of suitable materials. The body 58 has a substantiallycylindrical base 60 having a diameter that is sized to fit within theinterior diameter of a desired conduit. A plurality of fluid passages 62penetrate axially and completely through the base 60. In currentpreferred embodiments, there are eight fluid passages 62, althoughdepending on flow conditions there may be more or fewer than thatnumber. The diameter of the fluid passages must be sufficient at leastfor any solids that might be encountered to pass through the passages 62without obstruction. Preferably, the passages 62 have a much greaterdiameter than necessary for that purpose. However, the diameter of thepassages 62 is typically established to provide the pressure dropnecessary across the flow enhancer.

[0026] A dome 64 projects upwardly from the center of the cylindricalbase 60. The dome 64 has a smaller diameter than the base 60 so thatfluid may flow around the dome 64. In this embodiment, the dome 64includes a reduced diameter lower neck section 66 and an enlarged upperhead section 68 having a radial outer surface 70 that is substantiallyflat. The upper head section 68 also presents a substantially flat uppersurface 72.

[0027] The geometry of the components of the flow enhancer body 52 isimportant in terms of its functions for flow control. As FIG. 1indicates, fluid flow approaches the flow enhancer 50 from the upperend. Thus, the flat upper surface 72 advantageously encounters themajority of abrasive material that is carried in the fluid. Because theupper surface 72 is substantially flat, abrasive particles impingenormally to the surface 72. Therefore, the amount of abrasion and wearupon the upper surface 72 and the flow enhancer body 52 as a whole isminimized.

[0028]FIGS. 3 and 4 depict an alternative embodiment for a fluid flowenhancer 50′. For clarity, like components among the alternativeembodiments are numbered alike. In this embodiment, the dome 64′ has atapered side wall 74 extending from the rounded upper surface 72′downward to the base 60 so that the head section 68′ is smaller than theneck section 66′. There are indentations 78 in the tapered side wall 74that increase in width but decrease in depth as the base 60 isapproached. The indentations 78 extend upwardly from the side walls ofthe fluid passages 62 and, in use, provide an increased wear area uponwhich abrasives can act. This feature extends the life span of the fluidflow enhancer 50′ in resisting abrasion and wear around the openings 62.A primary advantage to this embodiment is that wear patterns are morebalanced as compared to the flow enhancer 50 described earlier becausethe radially internal portions of the fluid openings 62 of flow enhancer50′ are provided a greater exposure to the passing fluid. Thus, wearupon the flow enhancer 50′ is more even, and the wear enhancer 50′should not be required to be replaced as often.

[0029] FIGS. 5-7 illustrate a third embodiment for a fluid flow enhancer50″ that is currently the most highly preferred version. Fluid flowenhancer 50″ includes a recessed central valley 80 that results in thebase 60 presenting a raised peripheral rim 82. The dome 64 projectsupwardly from the recessed valley 80 but has a reduced height so thatits rounded upper surface 72″ is approximately level with the top of therim 82 (see FIG. 7). In this embodiment as well, the dome 64 has areduced diameter head section 68″ and a neck section 66″ with a somewhatlarger diameter, thereby resulting in a tapered side wall 74. Theadvantage associated with this embodiment of fluid flow enhancer is thatthe wear patterns surrounding the inlets of the fluid passages 62 arethe most balanced as between all three of the flow enhancers 50, 50′ and50″. As a result, it is expected that this design will have the longestlife span in operation.

[0030]FIG. 8 illustrates a pair of flow enhancers 50″a and 50″bpositioned in a staged or tandem relation within a flow conduit 86. Itis noted that the flow conduit 86 may be representative of a locationimmediately downstream from a choke valve choke mechanism, such as thechoke mechanism 23 described earlier. Alternatively, the flow conduit 86may be representative of any location within a pipe or other fluidconduit wherein it is desired to reduce fluid pressure. In that case,the flow enhancers 50″ are used as a stand-alone measure for fluidpressure reduction. The lower end 88 of the flow enhancer 50″b restsagainst a seat member 90 that is secured within the conduit 86. Atubular spacer element 92 is disposed between the upstream flow enhancer50″a and the downstream flow enhancer 50″b.

[0031] In operation, fluid is flowed through the conduit 86 in thedirection indicated by the arrows 94. In the upper portion 96 of theconduit 86, the fluid is under high pressure. Upon encountering theupstream flow enhancer 50″a, the fluid is directed through therestricted diameter fluid passages 62 of the flow enhancer 50″a, itspassage being assisted by the tapered side wall 74. Because a pressuredrop occurs across the upper flow enhancer 50″a, the fluid is at areduced pressure when it resides within area 98 of the conduit 86. Thefluid then encounters the downstream flow enhancer 50″b and is directedthrough its fluid passages 62. A second, staged pressure reductionoccurs across the downstream flow enhancer 50″b and, therefore, thefluid is at a further reduced pressure in area 100 of the conduit 86. Ifdesired, additional flow enhancers may be located downstream of flowenhancer 50″b to provide further staged pressure reductions.

[0032] While the invention has been shown in only some of its forms, itshould be apparent to those skilled in the art that it is not solimited, but is susceptible to various changes without departing fromthe scope of the invention.

What is claimed is:
 1. A fluid flow enhancer for reducing fluid pressurewithin a fluid conduit, the fluid flow enhancer comprising: a generallycylindrical base; a dome extending upwardly from a central portion ofthe base; and a plurality of fluid flow passages substantiallysurrounding the dome and disposed axially through the base.
 2. The fluidflow enhancer of claim 1 wherein the dome presents a lower reduceddiameter neck section and an upper enlarged diameter head section. 3.The fluid flow enhancer of claim 2 wherein the upper enlarged diameterhead section presents a substantially flat upper surface.
 4. The fluidflow enhancer of claim 1 wherein the dome presents a rounded uppersurface.
 5. The fluid flow enhancer of claim 1 wherein the dome presentsan enlarged diameter neck section and a reduced diameter head section.6. The fluid flow enhancer of claim 5 wherein the dome further comprisesa tapered side wall having a plurality of indentations that adjoin thefluid openings.
 7. The fluid flow enhancer of claim 1 wherein the basepresents an upwardly extending peripheral rim that defines a valleyradially within.
 8. The fluid flow enhancer of claim 7 wherein the uppersurface of the dome is approximately level with the rim.
 9. A chokevalve assembly for controlling and reducing fluid pressure within afluid conduit, the fluid flow choke valve assembly comprising: a fluidconduit; a choke mechanism within the fluid conduit for modulating fluidflow and creating a first fluid pressure reduction within the fluidconduit, the choke mechanism comprising: a flow cage having a pluralityof fluid openings therein; and a tip member mounted for linear movementwithin the flow cage and also having a plurality of fluid openingstherein that can be selectively aligned with the fluid openings in theflow cage to create opposing fluid jets within the choke mechanism; anda flow restrictor located within the fluid conduit downstream of thechoke mechanism for creating a fluid pressure drop within the fluidconduit.
 10. The choke valve assembly of claim 9 wherein the flowrestrictor comprises a generally cylindrical base and a dome projectingupwardly from a central portion of the base.
 11. The choke valveassembly of claim 10 wherein the flow restrictor further comprises aplurality of fluid passage disposed through the base.
 12. The chokevalve assembly of claim 10 wherein the dome presents a substantiallyflat upper surface to receive abrasives within fluid flowed within thefluid conduit.
 13. The choke valve assembly of claim 10 wherein the domecomprises a neck section and a head section, the head section having agreater diameter than the neck section.
 14. The choke valve assembly ofclaim 10 wherein the dome comprises a neck section and a head section,the head section having a smaller diameter than the neck section.
 15. Amethod of reducing fluid pressure within a fluid conduit comprising:disposing a first fluid restricting flow enhancer within a fluidconduit, the flow enhancer having a generally cylindrical base with aplurality of fluid passages disposed therethrough and a dome projectingupwardly from the base; flowing fluid through the fluid conduit and theflow enhancer to effect a pressure drop within the conduit across theenhancer; and receiving abrasives within the fluid conduit upon an upperwear surface of the dome.
 16. The method of claim 15 wherein theoperation of flowing fluid through the flow enhancer comprises flowingthe fluid through the plurality of fluid passages within the flowenhancer.
 17. The method of claim 15 wherein the operation of disposingthe fluid flow enhancer within a fluid conduit further compriseslocating the flow enhancer downstream and proximate a choke valve withinthe fluid conduit.
 18. The method of claim 15 further comprising theoperation of disposing a second fluid restricting flow enhancer withinthe fluid conduit in a staged relation to the first fluid flow enhancerto provide a second, staged fluid pressure reduction within the conduit.